Radiation detectors are devices capable of detecting incident radiation. In medicine, radiation detectors for X-ray images have applications for the diagnosis of a patient's condition. The radiation detectors for X-ray images are typically integrated in radiological instruments that utilize computer-processed X-ray images to produce images of specific regions of a patient's body. These images may be planar images, panoramic images or so-called tomographic images. Planar images are typically obtained by flat panel radiation detectors. Panoramic images may be obtained by a sequence of planar images taken one after another. Tomographic images may instead be obtained by a three-dimensional reconstruction of the specific regions of the patient's body. The radiological instruments may be intra-oral radiologic dental imagers, dental imagers, mammography systems, computed tomography scanners (CT-scanner), computed axial tomography scanners (CAT-scanners), mobile C-arm, etc. Indirect conversion radiation detectors for X-ray images may consist of a radiation converter element (e.g. a scintillator) that absorbs and converts the incident radiation (i.e. X-rays) into converted radiation with longer wavelength (e.g. visible light). The converted radiation with longer wavelength reaches a photo sensitive element, e.g. a CMOS photosensor, a CCD image sensor, etc. The photo sensitive element may be coupled to an electronic system that generates electrical signals corresponding to a radiation pattern of the incident radiation absorbed by the radiation converter element. Data embodied in such electrical signals may be shown in a visual display or sent to a computer for further analysis of the radiation pattern.
The converted radiation generated in the radiation converter element has a wide angular distribution, e.g. the radiation may be isotropically generated. As a consequence the converted radiation originated at one originating region of the radiation converter element in response to the incident radiation may be transmitted through the radiation converter element to a region of the photosensor far away from the originating region of the radiation converter element. This results in an undesired effect which is sometimes called in the art crosstalk or optical light spreading and may result in blurred X-ray images or X-ray images with less spatial resolution. Several solutions exist to prevent or limit crosstalk in radiation detectors.
For example US 2005/0111612 A1 discloses a Computed Tomography detector. The Computed Tomography detector (CT) includes a plurality of scintillators separated by gaps filled with reflectors, a photodiode array arranged below the plurality of scintillators and an optical layer mask comprising optical mask elements arranged between the plurality of scintillators and the photodiode array. The optical mask layer absorbs light and is designed to reduce lateral cross-talk from a scintillator and the photodiode of a neighboring scintillator.
The optical mask layer may contain optical reflective elements (or angled reflective elements) to reduce the lateral cross-talk between neighboring photodiodes.
However, reduction of the lateral cross-talk is limited to cross-talk between neighboring photodiode/scintillators cells. Further, reflectors between neighboring scintillators are required to reflect light converted in a scintillator cell that, without reflectors, would directly impinge via the gap on a neighboring photodiode. The latter situation could for example arise for large spreading of the converted light.